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GIANT MAGNETORESISTANCE IN ELECTRODEPOSITED MULTILAYER FILMS. THE INFLUENCE OF SUPERPARAMAGNETIC REGIONS

I. Bakonyi1,* , L. Péter1, V. Weihnacht1, J. Tóth1, L. F. Kiss1, C. M. Schneider2

Affiliation

  1. Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences H-1525 Budapest, P.O.B. 49, Hungary
  2. Leibniz Institute for Solid State Physics and Materials Research (IFW), Dresden, Germany

Abstract

When preparing an alternating sequence of magnetic (Co or Ni) and non-magnetic (Cu) layers by electrodeposition using the two-pulse plating technique, a dissolution of the less noble magnetic Co and Ni atoms can take place during the deposition of the more noble and non-magnetic Cu atoms. This process results in changes of the actual sublayer thicknesses with respect to the nominal values and can also cause some chemical intermixing at the magnetic/non-magnetic interfaces. As a consequence, superparamagnetic (SPM) regions with “loose magnetic moments” can form as has been demonstrated for electrodeposited Ni-Cu/Cu multilayers. We have also shown recently for electrodeposited Co-Cu/Cu multilayers that if some fraction of the magnetic layers exhibits SPM behaviour then the observed giant magnetoresistance (GMR) can be quantitatively decomposed into a ferromagnetic (FM) and a SPM contribution. In this paper, the results of a similar GMR decomposition study are presented for two electrodeposited Co-Cu/Cu multilayers. In the multilayer with strongly non-saturated magnetoresistance curves, the dominant GMR term was due to SPM regions, whereas in the other multilayer for which the magnetoresistance is mostly saturated in magnetic fields around 1 to 2 kOe, the FM contribution to the GMR is much larger. At the same time, magnetic measurements on the first multilayer sample have also revealed the presence of a large SPM contribution to the magnetization..

Keywords

Giant magnetoresistance (GMR), Superparamagnetism (SPM), Electrodeposited multilayers.

Submitted at: Aug. 18, 2004
Accepted at: March 23, 2005

Citation

I. Bakonyi, L. Péter, V. Weihnacht, J. Tóth, L. F. Kiss, C. M. Schneider, GIANT MAGNETORESISTANCE IN ELECTRODEPOSITED MULTILAYER FILMS. THE INFLUENCE OF SUPERPARAMAGNETIC REGIONS, Journal of Optoelectronics and Advanced Materials Vol. 7, Iss. 2, pp. 589-598 (2005)